1. Field of the Invention
The present invention relates to a telescopic tube and a telescopic writing pen, and more particularly to one having at least two metallic tubes in different diameters to change its length after retraction.
2. Description of the Prior Art
A metallic telescopic tube is widely used to an antenna of an electronic apparatus, a writing pen for a touch screen or a pointer. A conventional metallic tube has at least two metallic tubes in different diameters which are a small tube and a big tube. The small tube is fitted in the big tube. A limit mechanism is provided between the small tube and the big tube. A leaf spring is provided between the outer wall of the small tube and the inner wall of the big tube. When in use, the small tube is pulled or pushed with respect to the big tube to shorten or prolong its length. The leaf spring provides a damping effect to the sliding of the small tube. The limit mechanism provides a limit effect to the extension or retraction of the small tube. Due to the differences in size between the tubes and the leaf spring, this kind telescopic tube has the following shortcomings:
1. When the small tube is pulled or pushed with respect to the big tube, it is not easy to control its looseness and tightness. The quality of the products is unstable.
2. When the small tube is pulled or pushed with respect to the big tube, there will be friction noises produced by the leaf spring and the tubes.